Physiological mechanisms under special conditions:How do postural changes affect respiratory function? Takao IKEDA 1 , Masaya HIBINO 1 , Norimichi UENISHI 1 1Department of General Internal Medicine & Emergency Medicine Fujita Health University School of Medicine pp.37-46
Published Date 2020/1/1
DOI https://doi.org/10.11477/mf.3102200707
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Postural changes affect respiratory function through various physiological mechanisms such as the effect of gravity, changes in pulmonary blood flow, and the effectiveness of respiratory muscles. Compared to the supine position in healthy subjects breathing spontaneously, the upright position has a beneficial effect on respiratory function due to increased functional residual capacity, decreased airway resistance, increased static lung compliance, and increased cough effort. In mechanically ventilated patients, the head-up position has been shown to improve end-expiratory lung volume, airway resistance, work of breathing, and respiratory comfort. However, because there are many individual differences in these effects depending on the underlying pathology and overall patient status, careful monitoring after postural changes is important. In patients with ARDS, the prone position leads to homogenization of alveolar aeration and improvement of lung compliance by releasing compression of the dorsal part of the lung due to gravity and the ‘shape matching' effect on the ventral part of the lung. In addition, the dorsal predominance of pulmonary blood flow regardless of body position improves ventilation/perfusion matching and oxygenation. Learning about changes in the physiology of breathing due to postural changes can help to optimize the patient's postural position and identify important points for monitoring after these postural changes. In diseases presenting with characteristic symptoms such as orthopnea, platypnea, and trepopnea, knowledge of the underlying physiology gives clues to establish the diagnosis.

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